In practice, the correct tension of a filamentous element (e.g. racket string) passing in a zig-zag fashion through oval frame holes is considered very important to allow a player, when hitting a ball, such as a tennis ball, to direct the ball at a desired speed. The shot effect and direction are achieved by the player's ability, the correct string tension, and the configuration of grid squares (grate) formed by the interwoven racket strings.
During play, collisions between the ball and the racket strings often cause displacement of some sections of the strings and alter the grate configuration. An altered grate configuration acts as a tempered patch and produces an imbalance that impairs shot quality. It is for this reason that we often see players making great efforts to correct such defects with their fingers.
Another difficulty, typical of a racket sport, is observed when there is a cut in a non-central point of the string. The string's tension is essentially maintained due to frictional adjustment against the racket frame threading holes and crossings, but when there is a cut section, a tempering imbalance may occur that may bend the racket. Such bending may be temporarily corrected by making a compensating cut made at a certain, counter balancing point of the grate.
According to previous rules of the art, in order to solve the above-mentioned problems without stopping play or replacing the racket, tennis players require a lever at hand to correct the string displacement referred in the above former case, as well as a pair of scissors or a cutting element to solve the imbalance referred to in the above latter case. Obviously, the danger posed by such elements prevents tennis players from carrying such items to the tennis court.